Modular Snubberless Bidirectional Soft-switching Current-fed Dual 6-Pack (CFD6P) DC/DC Converter

This paper presents a modular snubberless bidirectional soft-switching current-fed dual 6-pack (CFD6P) dc/dc converter to interface two dc buses of 24V and 380V. It is therefore suitable for energy storage elements in UPS, renewable energy system, vehicle, and micro-grid applications. The proposed novel secondary-modulation technique forces the currents through the primary side (low voltage side) devices to reverse its direction resulting in zero current switching (ZCS) or natural commutation of current-fed low voltage side devices. Secondary side (high voltage side) devices are turned-on with zero voltage switching (ZVS). In addition, the resonance between the device parasitic capacitance and transformer leakage inductance achieves ZVS turn-on of the primary side devices. Thus, the converter maintains a zero voltage-zero current switching (ZVZCS) of the current-fed low voltage devices and ZVS of high voltage devices. As the applications requires high voltage conversion ratio, the current-fed technology achieves better voltage boost with reduced transformer turns ratio. Also, high current applications needs short circuit protection and that is built-in the converter inherently. It limits the peak current and circulating current through the devices resulting in low kVA rating devices. Steady-state operation, analysis, design of the proposed converter and the soft-switching conditions have been studied and explained. The proposed topology has been compared with current-fed three phase half bridge (CF-DAB3) analytically. The Simulation results using PSIM 9.3 have been illustrated to verify the analysis and design. Experimental results for 1kW laboratory prototype have been demonstrated as a proof-of-concept at present to validate the claims.